The present invention relates to a method and an apparatus for controlling the rise and fall of the temperature in a semiconductor substrate including as a silicon wafer when such semiconductor substrate is being subjected to treatments such as oxidization, diffusion or chemical vapor deposition.
Further, the present invention relates to a susceptor in a gas phase thin film growth apparatus and a gas phase thin film growth apparatus using such susceptor and more particularly to a susceptor which is capable of minimizing contamination of the semiconductor substrate caused by metal impurities at the time of effecting an air phase growth of a thin film and an apparatus using such susceptor.
The semiconductor substrate has a wide range of temperature rise/fall characteristics depending on materials, thickness and physical properties and, in other words, differs in the rate of temperature rise/fall and the in-plane temperature distribution.
Particularly, silicon wafers have different temperature rise/fall characteristics depending on the concentration of dopants including boron, phosphor and antimony.
Conventionally, the control of rising and falling semiconductor temperature at the time of oxidation, diffusion and chemical vapor deposition is done by feeding semiconductor substrates into a reactor set at an actual operating temperature, measuring the temperature of said semiconductor substrates to obtain temperature rise/fall characteristics of the respective semiconductor substrates, and then, writing respective temperature control programs on the basis of the thus obtained data for the temperature rise and fall control and using only a reactor installed with a specific temperature control program which suits a semiconductor having a specific temperature rising/falling characteristic.
According to the conventional method of temperature rise/fall control of the semiconductor substrate, however, a problem that a semiconductor substrate is subjected to a temperature rise/fall control on the basis of a specific temperature control program suited to a semiconductor substrate having a specific temperature rise/fall characteristic. If a wrong semiconductor substrate having a different temperature rise/fall characteristic is fed into the reactor to be heated on the basis of said specific temperature control program, a heat stress is exerted to said semiconductor substrate with the result that cracks can be formed in the semiconductor substrate leading to troubles such as damage to the components of the reactor, breakdown of the reactor, or the like. Such troubles are likely to cause production inefficiency and cost increase.
Therefore, the first object of the present invention is to provide a method and an apparatus for controlling the rise and fall of a semiconductor substrate which is free from any cracks in the semiconductor substrate even though the a semiconductor substrate having a different temperature rise/fall characteristic is fed into the reactor and the temperature is cause to rise and fall on the basis of the program install to the reactor.
Further, the gas phase thin film growth apparatus in which a thin film is gas phase grown on the semiconductor substrate such as a silicon wafer or the like has a structure as shown in FIG. 12.
More specifically, the conventional gas phase thin film growth apparatus is composed of a cylindrical reactor 31, a susceptor 32 provided in the lower inner part of said reactor 31 for holding a semiconductor substrate W such as a silicon wafer or the like, rotary drive means including a rotary shaft 33 and a motor (not shown) for rotating said susceptor 32 and a heater 34 for heating the semiconductor substrate W supported by said susceptor 34. Further, there are a plurality of exhaust gas pipes 35 provided at the bottom of said reactor 31 to discharge a leftover reaction gas, said exhaust gas pipes 35 being connected to the exhaust gas control system (not shown).
On the other hand, the upper part of the reactor 31 is provided with a plurality of gas supply pipes 36 to allow a reaction gas such as a material gas for producing the thin film and a carrier gas therefor into the reactor 31 and a disc shaped inflow gas guiding plate 37. Said admitted gas guiding plate 37 has a number of holes 37a therein to guide the gas flow.
Further, said susceptor 32 is disc-shaped and formed of a material such as carbon, silicon carbide, quartz or the like, with the upper surface thereof being formed with a seat recess for holding said semiconductor substrate therein as disclosed in Japanese Patent Application (Kokai) Publication No. 8-48595.
Further, while having said inflow gas guide plate 37 provided in the upper part of the reactor 31 so as to prevent the semiconductor substrate W from being contaminated by impurities such as whiled-up metal particles by suppressing an inflow of the atmosphere gas, said conventional gas phase thin film growth apparatus also has a cylindrical gas guiding member 8 so as to surround the lower area of a reverse side peripheral portion of said susceptor 2.
Thus constructed, the susceptor 32 holding the wafer substrate W thereon is rotated at a predetermined revolution by a motor drive in said conventional gas phase thin film growth apparatus. At this time, the wafer substrate W is rotated and heated by the heater 34 to the predetermined temperature. Also at the same time, the reaction gases such as a material gas and a carrier gas therefore are allowed into said reactor 31 by way of a plurality of gas supply pipes 36. With the reaction gases passing through said plurality of holes 37a in the inflow gas guide plate 37, the gas flow rate distribution within the reactor 31 is made uniform. The thus uniformly distributed reaction gases are supplied onto the semiconductor substrate W held on the susceptor 32 to gas phase grow into a thin film.
In said gas phase thin film growth apparatus, the atmosphere gases (reaction gases) cause particles to be whirled up in turbulences, adherents on the inner wall of the reactor to be accumulated or the semiconductor substrate to be contaminated with metal impurities. Therefore, it is essential to see that such whirl up of the particles, accumulation of adherents on the inner wall of the reactor or contamination of the substrate is suppressed such that contamination of the semiconductor substrate from metal impurities is prevented for minimizing the formation of crystal flaw in the thin film formed on the semiconductor substrate.
For this purpose, said gas phase thin film growth apparatus is provided with the above mentioned inflow gas guide plate 37 in the upper part of the reactor and the cylindrical gas guiding member 38 to surround the lower area of the space around the susceptor.
As a result, the turbulence of the atmosphere gas (the reaction gas) in the upper and lower areas of the space beneath the susceptor 32 is suppressed, thus preventing the particles from whirling up and the semiconductor substrate from being contaminated by metal impurities.
In this connection, as shown in FIG. 13 and FIG. 14, the rotated susceptor causes a flow of the atmosphere gas flow (gas flow) to generate from the central area to the peripheral area of the susceptor 32 as shown in arrow on the reverse side of the susceptor 32. In this connection, it is noted that FIGS. 13 and 14 are fragmental sectional views of the peripheral area of the susceptor 32; FIG. 13 shows the gas deflector 38 is formed at the peripheral area of the susceptor 32 on the reverse side thereof whereas FIG. 14 shows the gas deflector 38 is formed over the entire reverse side of the susceptor 32.
The flow of said atmosphere gas (gas flow) is generated by the centrifugal force caused by the rotation of the susceptor 32 and the viscosity of the gas. Such gas flow is sucked from the lower peripheral area of the wall and from near the bottom of the reactor 31 to rise along the periphery of the rotary shaft 33 until flowing out from between the reverse side of said susceptor 32 and the upper part of the gas deflector 38.
Therefore, said gas flow comes into contact with the internal lower portion components of the reactor 31 and the motor or the like which rotates to drive the rotary shaft 33, resulting in the mingling of the particles and metal impurities with the gas flow.
Said gas flow rises along the peripheral area of the susceptor after coming out the susceptor reverse side. Further, said gas flow reaches the surface of the semiconductor substrate W to cause the semiconductor substrate W to be contaminated by said gas flow containing the metal impurities.
Due to high integration of semiconductors, a higher and higher quality is being required for semiconductor substrates. Given the situation, such contamination as observed in the formation of the thin film on the semiconductor substrate poses the problem of degradation of the quality of the semiconductor substrates at the production process thereof.
The present invention is made in order to solve the above discussed problems of the prior art. Therefore, the primary object of the invention is to provide a method of and apparatus for controlling the rise and fall of the temperature in a semiconductor substrate which will not cause cracks or the like to be formed in the semiconductor substrate even if a wrong semiconductor substrate having a different temperature rise/fall characteristics.
Further the second object of the invention is to provide a susceptor of the gas phase growth apparatus which is capable of reducing the contamination by an atmosphere gas containing particles and metal impurities from the reverse side of the susceptor for the semiconductor substrate at the time of forming a thin film on the semiconductor substrate.
Still further, the third object of the invention is to provide a gas phase thin film growth apparatus which is capable of producing a high quality semiconductor substrate therein by effectively using said susceptor.
In order to solve the above-mentioned problem and realize the first object of the invention, the method of controlling the rising and falling temperature in a semiconductor substrate essentially comprises, in one aspect of the invention, the steps of writing one or a plurality of temperature control programs in advance adaptable for a variety of semiconductor substrates having different temperature rise/fall characteristics in preparation for the case where the control of a rising and falling temperature in the semiconductor substrate is effected as needed while the semiconductor substrate is subjected to an oxidation, diffusion, or chemical vapor deposition process; measuring temperatures in a plurality of locations in said semiconductor substrate after a passage of a predetermined time period since the semiconductor substrate is fed into a reactor set a predetermined temperature to obtain measured values; computing a rate of temperature rise and a distribution range of in-plane temperatures thereof out of said measured values to determine a temperature rise/fall characteristics thereof; selecting a temperature control program adaptable for said determined temperature rise/fall characteristics out of said one or a plurality of temperature control programs written in advance; and controlling the rise and fall of said semiconductor substrate in accordance with said selected temperature control programs.
The method of controlling the rise and fall of the temperature comprises, in a second aspect of the invention, the steps of writing a variety of temperature control programs in advance adaptable for a variety of semiconductor substrates having different temperature rise/fall characteristics in preparation for the case where the control of a rising and falling temperature in the semiconductor substrate is effected as needed while the semiconductor substrate is subjected to an oxidation, diffusion, or chemical vapor deposition process; measuring infra-red absorption coefficients of semiconductor substrates before or after each semiconductor substrate is fed into a reactor set at a predetermined temperature to obtain a measured value; computing a rate of temperature rise and a distribution range of in-plane temperatures thereof to determine a temperature rise/fall characteristics thereof; automatically selecting a temperature control program adaptable for said determined temperature rise/fall characteristics out of said one or a plurality of temperature control programs written in advance; and controlling the rise and fall of said semiconductor substrate in accordance with said selected temperature control programs.
On the other hand, the apparatus of controlling the rise and fall of the temperature in a semiconductor substrate essentially comprises, in one aspect of the invention, a reactor in which a semiconductor substrate is subjected to an oxidation, diffusion, or a chemical vapor deposition process; a disc-shaped horizontal heater provided at a lower portion of said processing vessel; a susceptor rotatably provided above said heater to horizontally hold said semiconductor substrate thereon; at least three hoisting pins to horizontally support said semiconductor substrate when fed into said reactor and and semiconductor substrate on said susceptor; a plurality of thermometers provided at the upper portion of the reactor to measure the temperature of the semiconductor substrate; means for determining the rising and falling temperature characteristic by inputting values measured by said thermometers to compute the rate of temperature rise and the range of in-plane temperature distribution in a predetermined time period; and a heater output control means for controlling an output of said disc-shaped horizontal heater by storing a variety of temperature control programs written in advance in correspondence with a variety of semiconductor substrates having different rising and falling temperature characteristics, selecting a temperature control program adaptable for the temperature rising and falling characteristic determined by said means for the rising and falling temperature characteristics out of said variety of temperature control programs prepared in advance, and inputting the measured values for the substrate thermometers based on the selected temperature control program.
Further, the apparatus of controlling the rise and fall of the temperature in a semiconductor substrate essentially comprises, in second aspect of the invention, a reactor in which a semiconductor substrate is subjected to an oxidation, diffusion, or a chemical vapor deposition process; a disc-shaped horizontal heater provided at a lower portion of said processing vessel; a susceptor rotatably provided above said heater to horizontally hold said semiconductor substrate thereon; at least three hoisting pins to horizontally support said semiconductor substrate when fed into said reactor and semiconductor substrate on said susceptor; a plurality of thermometers provided at the upper portion of the reactor to measure the temperature of the semiconductor substrate; a cassette provided beside the reactor and loaded with a number of semiconductor substrates in a plurality of layers; a transfer unit to transfer said semiconductor substrates from said cassette to the upper portion of said processing vessel; infrared absorption coefficient meters provided along the transfer passage of said semiconductor substrates from the position of discharge thereof from the cassette to the position of loading thereof onto the hoisting pins; means for determining the rising and falling temperature characteristic by inputting values measured by said infrared absorption coefficient meter to presume the rate of temperature rise and the range of in-plane temperature distribution in a predetermined time period; and a heater output control means for controlling an output of said disc-shaped horizontal heater by storing a variety of temperature control programs prepared in advance in correspondence with a variety of semiconductor substrates having different rising and falling temperature characteristics, selecting a temperature control program adaptable for the temperature rising and falling characteristic determined by said means for the rising and falling temperature characteristics out of said variety of temperature control programs prepared in advance, and inputting the measured values for the substrate thermometers based on the selected temperature control program.
It is preferable that said thermometer is an infrared rays irradiating thermometer.
In the first method of controlling the rising and falling temperature in the semiconductor substrate and the apparatus therefor, the temperature rise/fall characteristic of the semiconductor substrate is determined after the feed thereof into the reactor, a temperature control program adaptable for the determined temperature rise/fall characteristic of the semiconductor substrate is selected out of one or a plurality of temperature control programs written in advance, and the heater output is controlled based thereon to cause the temperature to rise and fall.
Further, in the second method of controlling the rising and falling temperature in the semiconductor substrate and the apparatus therefor, a temperature rise/fall characteristic of the semiconductor substrate is deteremined upon or after the admittance thereof into the reactor, a temperature control program adaptable for the determined rise/fall characteristic of the semiconductor substrate is selected out of a variety of temperature control programs written in advance, and the heater output is controlled based thereon to cause the temperature to rise and fall.
In order to attain the second object of the present invention, the sesceptor of the gas phase thin film growth apparatus according to the present invention is placed on the upper surface of said susceptor rotatably within the gas phase thin film growth apparatus and the reverse side of said susceptor is formed at a peripheral portion thereof with a gas flow deflector jutting from the reverse side thereof such that an atmosphere gas flow moving at the time of the rotation of the susceptor from the center thereof to the peripheral portion thereof is deflected downwardly by said gas flow deflector.
In this way, the provision of said gas flow deflector e at the peripheral portion on the reverse side of the susceptor facilitates that an impurities containing atmosphere gas flow generated by the susceptor rotation to move from the central portion to the peripheral portion over the reverse side thereof is deflected downwardly at the peripheral portion of the reverse side of the susceptor.
As a result, said gas flow will not reach the surface of the semiconductor substrate, thus, assuring the production of a high quality thin film.
In this connection, it is preferable that said gas flow deflector is in the form of an annular wall jutting downwardly from the peripheral portion of the reverse side of the susceptor.
In this way, the provision of the annular wall jutting downwardly from the peripheral portion of the reverse side of the susceptor facilitates that the impurities containing atmosphere gas flow moving from the central portion to the peripheral portion over the reverse side thereof is deflected downwardly from the peripheral portion of the susceptor reverse side.
Further, it is preferable that the formation of the annular wall integral with the susceptor eliminates the need for assembling work thereof on the susceptor.
Further, it is preferable that the provision of the annular wall having a curved inner face or a slant face therein helps a smooth downward deflection of the gas flow, thus suppressing the turbulence of the gas flow which is otherwise likely to be produced at the time of deflection thereof.
The gas phase thin film growth apparatus according to the present invention comprises a reactor; a susceptor rotatably placed on the upper surface of the semiconductor within the reactor; a deflector jutting downwardly from the peripheral portion of the reverse side of the susceptor; rotary drive means for rotating said susceptor; heating means for heating the semiconductor substrate placed on the upper surface of the susceptor; means for charging into the reactor a reaction gas containing a material gas to form a thin film on the semiconductor substrate; and exhaust means for discharging a leftover reaction gas in the reactor such that said deflector in the susceptor is adapted to cause an atmosphere gas flow flowing from the center portion to the peripheral portion over the reverse side of susceptor at the time of rotation thereof to be deflected downwardly.
In this way, the provision of the deflector at the reverse peripheral portion of the susceptor causes an impurities containing atmosphere gas flowing from the central portion to the peripheral portion over the reverse side to be deflected downwardly from the reverse peripheral portion thereof.
As a result, said gas flow will not reach the surface of the semiconductor substrate placed on the upper face of the susceptor, thus assuring the formation of high quality thin films.
In this connection, it is preferable that there is provided a gas flow guide member below the underside of the susceptor, said gas flow guide member having an upper end in the proximity of said gas flow deflector of the susceptor.
In this way, the provision of the gas flow guide member such that said gas flow guide member surrounds an area below the susceptor is preferable, in view of preventing the impurities containing gas from reaching the surface of the semiconductor substrate and forming a high quality thin film on said semiconductor substrate.
Further, it is preferable that said deflector is an annular wall jutting downwardly from the reverse peripheral portion of the susceptor.